Since a thrust ball bearing is configured such that a shaft washer and a housing washer are separable from each other, it is necessary to ensure that balls do not easily fall out from the cage in view of ease of handling such as attachment and detachment of the bearing to and from a device.
A copper alloy machined cage is known as a cage used in a thrust ball bearing. As shown in FIG. 7, a conventional copper alloy machined cage 100 has a shape in which one side of a pocket 101 holds a ball 102 in a truncated cone shape, and the other side thereof is cylindrical. Since it is easy for the ball 102 to fall out in this state when the ball 102 is placed into the pocket 101 from the cylindrical side, the periphery of the pocket 101 is swaged at four positions P after placing the ball 102 in the case 100 to prevent the ball 102 from falling out.
Further, there has been proposed a resin cage in which an entrance diameter of a cage pocket is set to be smaller than a ball diameter, and in which ball is placed through elastic deformation (for example, refer to Patent Document 1 and Patent Document 2).